This application claims the priority of German Application No. 196 45 826.9 filed Nov. 7, 1996, which is incorporated herein by reference.
Internal-combustion engines, particularly of the reciprocating piston type are increasingly provided with electrically triggered and/or operated actuators for a great variety of engine functions. Such actuators are operated by means of at least one power unit of an integrated electronic engine control system which senses the control-relevant operational data of the engine by means of sensors.
To be able to perform tests and investigations of the individual engine functions during engine run, a great variety of parameters, such as the moment of ignition, the injected fuel quantity, the moment of injection, operating times of the cylinder valvesxe2x80x94to name only the most important onesxe2x80x94have to be predetermined and must be changeable. Previously, such operations have been carried out, among others, by disconnecting the integrated electronic engine control system and replacing it by an external engine control system. Such a conventional switchover measure has to be performed, however, during a standstill of the engine and is therefore very time consuming.
It is an object of the invention to provide an improved method of the above-outlined kind with which the discussed engine tests may be performed during engine run and which, at the same time, offers the possibility of externally interfering with the control of selected engine functions.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the method of controlling functions of an internal-combustion engine having electrically operated actuators for controlling engine functions, includes the following steps: detecting control-relevant operational data by a sensor arrangement; applying the detected operational data to a first, engine-integrated electronic engine control system; controlling the actuators by control signals from the first electronic engine control system through a power unit; applying the operational data to a second, external electronic engine control system in synchronism with the operational data applied to the first electronic engine control system; generating control signals at an output of the second electronic engine control system; applying, to the power unit, control signals emanating from the second electronic engine control system for the actuator of at least one selected engine function; and simultaneously with the preceding step, removing from the power unit control signals emanating from the first electronic engine control system for the actuator serving the selected engine function. As a result, engine control is simultaneously effected by the first and second electronic engine control systems such that the selected engine function is controlled by the second electronic engine control system and the remaining engine functions are controlled by the first electronic engine control system.
The particular advantage of the invention as outlined above resides in that during tests not all signals necessary for the overall engine operation are switched over to the external engine control system which would then take over the entire engine operation, but only those which are required for the examination of the selected engine functions. For example, for examining variations of the moment of ignition, only the signals required for the ignition are switched over to the external engine control system, while the control of the injection and all other operational functions of the engine continue to be controlled by the engine""s own integrated engine control system. Conversely, the moment of injection and quantity of injected fuel may be varied by the external engine control system, while the ignition continues to be controlled by the integrated engine control system.
In the above-outlined method according to the invention individual or groupwise selected engine functions may be controlled and varied by the external engine control system. Engine functions which may be handled in this manner are, for example, the exhaust gas reintroduction, the idling regulation, and the change of the valve control times of electromagnetically operated cylinder valves. Additional functions, such as the control of an air conditioning unit, a fan or the like may also be considered as engine functions as far as the present invention is concerned. It is always feasible to direct the engine operation generally by the integrated engine control system and to direct only the selected engine function from the external engine control system which is expediently freely programmable. Thus, the method according to the invention offers not only the possibility for an optimized operation but also provides an excellent opportunity for a direct comparison between the different engine controls to thus find and directly test possible improvement potentials without circumstantial restructuring work.
According to a particularly advantageous feature of the invention, the deactivation of the control signals of the integrated engine control system and the activation of the corresponding control signals of the external engine control system are effected at a moment when no control signals are present at the outputs of either engine control system. In this connection the fact is advantageously utilized that particularly in reciprocating piston engines practically all actuators are periodically operated, so that periods are always available in which at least the selected actuator is idle. If the switchover is effected in a period between two control signals, a switchover in a running engine is achieved without adversely interfering with the engine operation.